The present invention relates generally to peer-to-peer remote copy (PPRC) methods and systems and, more particularly, to a method and system for performing automatic stand alone recovery of secondary storage volumes for peer to peer remote copy (PPRC) operations.
With increasingly large amounts of data being handled in data processing systems, storage systems, such as disk storage systems are being used to store data. Some organizations rely heavily on data and quick access to the data. Disasters caused by environmental conditions, user errors, or application errors may occur in which access to the data is lost for some period of time. Mirroring or copying data to a secondary storage system from a primary storage system is currently employed to minimize the time in which access to data is lost due to a disaster.
Peer-to-peer remote copy (PPRC) is a synchronous copy mechanism that creates a copy of data at a remote or secondary storage system. This copy, at the secondary storage system, is kept current with the data located at the primary storage system. In other words, a copy of the data located at the secondary storage system is kept in sync with the data at the primary storage system as observed by the user of the data. Volume pairs are designated in which a volume in the primary storage system is paired with a volume in the secondary storage system.
With a PPRC system, a PPRC data copy to the recovery or secondary storage system occurs synchronously from the primary host point of view with write operations to volumes in the primary storage system. Paths connect the primary storage system to the secondary storage system. When data is written from a primary host to the primary storage system, the data written to a primary volume is also written by the primary storage system to a corresponding volume in the secondary storage system using a path to the secondary storage system.
In effect, the primary volume data is replicated to a corresponding secondary volume and the two volumes are kept in sync when writes are sent to the primary volume. It is the responsibility of the primary storage system to send all primary volume writes to the corresponding secondary volume of the secondary storage system. It is the responsibility of the secondary storage system to disallow any read or write accesses by any hosts to the secondary volume while the secondary volume is dedicated as secondary storage. These actions keep the content of the primary and secondary volumes identical.
When access to the primary volume data of the primary storage system is lost, the secondary volume data of the secondary storage system is needed for recovery. In current peer to peer remote copy (PPRC) operations, issuing a xe2x80x9crecoverxe2x80x9d command from a host to a secondary volume of the secondary storage system allows read/write access to the secondary volume. The recover commands tell the secondary storage system that the PPRC primary and secondary volume pair relationships are terminated and that a host can have full access to the secondary volumes in the secondary storage system.
With this approach there has to be a secondary host connected to the secondary storage system to issue the recover commands. In effect, there has to be at least one volume of the secondary storage system accessible to the secondary host. This is a problem because many users desire a host at the remote secondary storage system site be connected to the secondary storage system only during a recovery operation. Many users also desire all of the volumes of the secondary storage system to be available as secondary volumes for PPRC operations and do not want to have at least one volume restricted for secondary host access during PPRC operations.
A problem is that a remote host cannot access the secondary volumes until the remote host issues the recover commands. The recover commands cannot be issued until the secondary volumes are online. To bring a volume online requires read/write commands that are rejected by the secondary storage system while the volumes of the secondary storage system are secondary storage volumes. Consequently, a secondary host has to be connected to the secondary storage system at all times including recovery and non-recovery time periods. What is needed is a method and system for performing automatic stand alone recovery of secondary volumes for peer to peer remote copy (PPRC) operations such that a host does not need to be connected to the secondary storage system.
Accordingly, it is an object of the present invention to provide a method and system for performing automatic stand alone recovery of secondary volumes for PPRC operations.
It is another object of the present invention to provide a method and system for performing automatic stand alone recovery of secondary volumes for PPRC operations such that a host does not need to be connected to the secondary storage system.
It is a further object of the present invention to provide a method and system for performing automatic data stand alone data recovery of secondary volumes for PPRC operations such that none of the volumes of a secondary storage system have to be accessible to the secondary host during PPRC operations and, as a result, all volumes of the secondary storage system are available to be secondary volumes.
In carrying out the above objects and other objects, the present invention provides a method for use in a PPRC system having a primary storage system including storage volumes and a secondary storage system including storage volumes. The storage volumes of the primary storage system correspond to respective storage volumes of the secondary storage system to form established PPRC storage volume pairs in which data written on primary storage volumes is automatically written on to the corresponding secondary storage volumes. The storage volumes of the secondary storage system that are part of the established PPRC storage volume pairs are only accessible to receive the data written on to the corresponding primary storage volume. The method makes data available from established PPRC storage volumes of the secondary storage system. The method includes isolating the secondary storage system to be in a stand alone state such that access from any storage systems and hosts is prevented. It is then determined if each storage volume of the secondary storage system is part of an established PPRC storage volume pair. Each established PPRC storage volume pair is then terminated such that the storage volumes of the secondary storage system that are part of the established PPRC storage volume pairs are accessible to hosts. The secondary storage system is then made available to hosts to effect data recovery of the established PPRC storage volumes.
In carrying out the above objects and other objects, the present invention further provides a peer to peer remote copy system in accordance with the method of the present invention.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the present invention when taken in connection with the accompanying drawings.